Sojibo frank seibitya



June 17, 1930. 5. F. SHIBUYA 1,764,531

'ANGLE TRISEC'IOR Filed July 27, 1929 INVENTOR.

ATTORNEYS.

Patented June 17, 1939 SOJIRO FnAnKsnIBuYA, or sanrnnnorsoo oALiFonnIA ANGLE crnrsnoron Application filed July 27, 1929. Serial no. 1,507;

My invention relates to improvements in angle trisectors and it consists in the combinations, constructions and arrangements hereinafter described and claimed.

An obect of my invention is to provide an improvement over that form of the device shown in my co-pending application filed January 23rd, 1929, Serial No. 384,567. In the present device, the curved edge used for determining one-third of the angle in question is graduated so as to give the proper point location for angles ranging between zero degrees to 180 degrees. This marking of the device saves considerable time in trisecting an angle.

Other objects and advantages will appear in the following specification, and the novel features of the device Will be particularly pointed out in the appended claims.

My invention is illustrated in the acv companying drawing forming a part of this application, in which Figure 1 is a plan view of the device;

Figure 2 illustrates how the trisector i curve is obtained; and

Figure 3 shows how the markings on the trisector curve are obtained.

It is best to show how the device is made and how the particular trisector curve is 8 arrived at. Referring "to Figure 1, it will be noted that a protractor 1 has a radiallyextending arm 2 projecting from its periphery. The edge 3, of this arm is perpendicular to the edge a of the protractor and is in line with the center 5 of the protractor.

A curved arm 8 projects from the protractor and terminates in the arm 2. The edge 7' of this arm extends from the sixty degree marl: on the protractor and terminates on the edge 3 at the point 8. The curved edge? is predetermined and is obtained in a manner hereinafter described. -VVith this curve any angle up to one hundred and eighty degrees can be trisec'ted'.

The trisector 9 shown in Figure AI is cut out of the piece projecting from the protractor 1. The ed e forms to the edge 19 conform to the first form.

edges 3 and 13 of the i 10 ofthis piece conand the edges 11 and I will now describe how the curved edge 7 is determined. .In Figure 2, I draw a line AB equal to the-"distance between points 14] and 15 on the trisector shown in Figurel. v j l i I The line A-B is bisected at 0 and perpendicular O 'i-K" is" drawn from this point. The are A,'B.is now drawn and points M and D sixty degrees apart and: sixtydegrees -fromthe points. A and B are located. This will leave the arc K-D equal to one-third of the, arc Ajwlid The are KD is divided into a number of equal parts designated by the: letter X. The drawing shows eight equal parts. In like manner, the arc A-K'isdivided into eight equal parts designated by the letter Y. i Arc X is equalto one third of thearc Y. i

With the radius OB and the points G as centers inthe arc, A K, arcs G are drawn. Withthe same radius butwith the points Eon the arc K D as centers, arcs E are drawn, these intersecting the arcs G to form a number of points M, A curved line M-L is now drawn through all of the points M, and this curvedline is the one corresponding to the curved edges 7 and 10.

I have described how the curved edge 7 is determined. I will now show how the markings from'zero to ISOQdegreeson the curved edge are obtained. In Figure 3, I show thep'eiiphery of the protractor, 1 as havinga number of lines 16, extending radially therefrom. These lines are numbered from to 180 and represent various an gles having equivalent numbered degrees. For example, the line 180. coincides with the edge 4 and passes through the center 5. The lined-70 is placed five degrees up on the protractorfand passesi'to the center'S and then on through to five degrees up on the opposite side of the protractor'. The angle ,passes through the ten degree mark on one side 01% the protractorandthrough' the degree mark on the other side, the vertex of this angle being positioned at the center 5. 1 V a 7 lVith the point ltas a center and a radius equal to the distance between this point and the center 5, an are 17 may beinscribed on the curved arm 6. This are will intersect the sixty degree mark onthe protractor 1. This gives us 180 degrees, and it will be noted that Figures 1 and 3 are marked accordingly.

In like manner, arcs are struck from the intersection of the lines 16 with the periphcry of the protractor as centers, and the resulting marks 17 on the arm 6 are numa bered as shown in Figures 1 and 3. I From the foregoing d'escription of theva rious parts of the device, the operation thereof may be readily understood. A

Assuming that the angle RST, Figure 1, is to be trisected, This angle is first bisected by the line J S. The device is now laid upon the angle EST to determine its number of degrees. In the present instance, I have shown an angle of sixty degrees. The center 5 oi the protractor is placed on the vertex 5 and the edge 3 is coincided with the line JS. A mark is made upon the sheet of paper containing the angle RST opposite the number sixty on the arm 6 and adjacent to the edge 7. This mark or point can now be connected to the vertex S by the line QS. Theresulting angle ESQ, is

onethird of the angle RST.

' Although I have shown and described one embodiment of my'invention, it is to be understood that the same is susceptible of va rious changes, and I reserve the right to employ such changes as may come within the scopeof the appended claims.

I claim: I

1. A trisector for an angle having a semicircular shaped member, a radially-extend ing arm projecting from said member, and

a curved arm having'its endssecured' to the semi-circular member and the tree end of said radially-extending arm, the inner edge of curved arm being shaped in a predetermined manner for use in trisecting angles, said curved arm having markings thereon for indicating theproper point for trisecting the angle.

2. A device for trisecting angles comprising a-protractor, a radially-extending arm extending from said protractor and having one edge terminating atthe ninety degree mark on the protractor, a curved arm extending from the protractor to the free end of said first-named arm, the inneredge of said curved arm starting from the sixty del gree mark on the protractor, said curve being prearranged for use in the trisection of an angle, said curved arm having markings thereon for indicating the proper point for trisecting the angle.

SOJIRO FRANK SHIB'UYA. 

